Process of preparing carbon for electrical resistances.



UNITED STATES UKUOO [\Lf LnuwL PATENT OFFICE.

EDWARD GEORGE RIVERS, 0F RICHMOND, ENGLAND, ASSIGNOR OF ONE- HALF TO THE ELECTRIC AND ORDNANCE ACCESSORIES COMPANY LIMITED, OF BIRMINGHAM, ENGLAND.

PROCESS OF PREPARING CARBON FOR ELECTRICAL RESISTANCES.

Specification of Letters Patent.

Application filed December 22, 1905. Serial No. 293,039.

To allwhom it may concern.-

Be it known that I, EDWARD GEORGE RIV- ERS, civil engineer, a subject of the .Kin of Great Britain, residing at Beverley Lodge, Richmond, in the county of Surrey, England, have invented a certain new and useful Proc ess of Preparing Carbon for Electrical Resistances and the Like, of which the following is a specification.

This invention has reference to a process or method of preparing or treating carbon for use in the formation of electrical resistances and heater elements and as a paste for mounting and jointing electrical conductors for joining up platinum wires with carbon filaments in the manufacture of incandescent electric lamps and for analogous uses.

Hitherto it has been the resistance materia in the elements of electrical radiators and heaters finely ground, powdered, or deposited carbon inclosed between plates or concentric tubes of enameled iron; but the carbon applied or used in this form has not been commercially successful, principally by reason of the cost of production and the difficulty of insuring the permanence of initial tests as to current consumption.

According to the present invention these difficulties are obviated, a material of high resistance efficiency is obtained Without otherwise afiecting its conductivity, and the utilization of the resistance material in the manufacture of electrical radiator and heater elements is facilitated for electrical jointin and similar purposes by a process or metho of treatment which consists, broadly, in reassembling or re'conversion of the finely-powdered carbon into a solid body of high resistance mforming the said carbon into a paste with some alkaline silicious ag lutinate, such as a 801mm- 'lass and then subjmmixture to a j gfl' i emperature, and also, in cases where extreme hardness is required, to the subsequent action of a solution of carbonic acid or other weak acid which will act upon and decomne enaslica 'n' carryingmt the invention in its appli- 5o cation to the manufacture of the resistance elements of electrical radiators and other purposes finely-powdered r ort-carbon is mixed with a solution of so ublc SI 10a inany duced is subsequently proposed to utilize as Patented J an. 15, 1907.

ascertained or suitable proportions, accord efliciency desired. For instance. equal parts of soluble silica and water may be taken to iorm the levigating solution, which is mixed with the carbon in the proportions of one ounce of the said solution. to every two ounces of the carbon. The paste thus prodried and afterward sub ected to avert high temperature, with the result that by t I T. 'f'upon the agglutinate the mass hardens, and if the paste should be heated in contact with a body containing silica, such as an uiiglazedtile, it will adhere closely to the latter and does not exhibit the least tendency to disrupt either during the heating process'or afterward when subjected to high temperatures. It has been proved by, test and experiment that the electrical resistance of this siliciously-assembled carbon considerably exceeds that of hard arc carbon, a rod of which twelve inches in length and threeeighths of an inch in diameter is found to be practically about one ohm, whereas the resistance of a similar rod of the reassembled and prepared carbon is approximately 4.2 ohms, and the degree ofhardness which it ultimately attains when thoroughly set or fixed is sufficient for all practical purposes, inasmuch that glass-paper has only a slight effect upon it and a smooth file is re uired to abrade the surface to any materia degree. Further, it is not affected by any variations of temperature nor bv moisture, as the drying of the paste has the effect of settling and hardenin the mass in a manner similar to that in which hydraulic cements are set and hardened by the action of water. The fur, ther hardening of the set mass when re 'quired for special purposes is effected by im mersing the carbon, together with its support, in a solution of (70 or other weak acid.

In making up radiator resistance units or elements in whlch the repared carbon forms the resistance materia each unit is made up of a pair of vitrified stoneware or fire-clay tiles or other suitable refractory insulating material adapted to be bolted together at the corners, and one of them is provided upon the inner side with a shallow sinking of suitable depth to contain the carbon paste, while the inner face of the other tile is plain or fiat.

The sinking or recess in the one tile carries the paste, and the charged tile is heated in a (lryin -oven to a moderate temperature to dry t e mixture. The dried paste in-this condition is amenable to the action of glasspaper and so that current adjustment can e made by passing a current of known voltage through the mass and removing the material at the surface until a low-reading ammeter indicates that the current capacity has been reduced to the required standard.

may be effected by clamping thin copper strips between the tiles, so that their inner ends will touch the carbon.-

In cases where the element requires to be subjected to the action of CO solution or other weak acid to obtain extreme hardness the tile and hardened and self-attached block of siliciously-assembled carbon are immersed togetherinto a bath of the acid and allowedto remam until the resultant effervescence' ceases.

The invention is 'not limited to the one particular method herein described of makmg up the reassembled carbon into resistance elements, as the agglutinated carbon may be applied, either prior to or after heating, in-a variety of ways, according to the particular nature or purpose for which it is to be used; neither is 1t necessary in some cases to use a second tile as a cover to the tile carrying carbon.

Having fully described my invention, what I desire to claim and secure by Letters Patent is 1. The herein-described process of preparing carbon for electrical resistances, &c., consisting in mixing powdered carbon with an alkaline silicious agglutinate, and setting and hardening the resultant paste by sub jecting the same to a high temperature.

2. The herein-described process of prepar ing carbon for electrical resistances, &c., consisting in mixing powdered carbon with an alkaline silicious agglutinate, setting and hardening the resultant. paste by subjecting the same to a high temperature, and increasing the hardness by submitting the product to the action of a weak acid solution.

3. The herein-described process for forming electrical resistanceelements for radiators and other rises, consisting in producing a paste from powdered carbon and a silicious agglutinate, applying this paste to tiles of fire-clay, stoneware or other refractory insulating material containin silica, and collectively heating the fire-c ay, stoneware or other refractory material and paste applied thereto. I

4., The herein-described electrical resistance material consisting of hardened powdered carbon and an alkaline silicious agglutinate. i v I In testimony whereof I have hereunto set my hand in presence of two subscribing wit-.-

nesses.

EDWARD GEORGE RIVERS.

Witnesses:

ARTHUR DATOR, H. D. JAMESON 

